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connect prevent_purge,localhost,root,,;
START TRANSACTION WITH CONSISTENT SNAPSHOT;
connection default;
SET GLOBAL innodb_monitor_disable='all';
SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
CREATE TABLE `t` (a INT PRIMARY KEY) engine=InnoDB STATS_PERSISTENT=0;
INSERT INTO t VALUES (5);
SELECT name, count FROM information_schema.innodb_metrics
WHERE name ='lock_row_lock_current_waits';
name count
lock_row_lock_current_waits 0
connect con1,localhost,root,,;
BEGIN;
SELECT * FROM t FOR UPDATE;
a
5
connect con2,localhost,root,,;
SET DEBUG_SYNC="lock_wait_before_suspend SIGNAL blocked WAIT_FOR cont";
BEGIN;
SELECT * FROM t FOR UPDATE;
connection default;
SET DEBUG_SYNC="now WAIT_FOR blocked";
SELECT name, count FROM information_schema.innodb_metrics
WHERE name ='lock_row_lock_current_waits';
name count
lock_row_lock_current_waits 1
SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
SELECT name, count FROM information_schema.innodb_metrics
WHERE name ='lock_row_lock_current_waits';
name count
lock_row_lock_current_waits 1
SET DEBUG_SYNC="now SIGNAL cont";
disconnect con1;
connection con2;
a
5
COMMIT;
disconnect con2;
connection default;
SET DEBUG_SYNC="reset";
SELECT name, count FROM information_schema.innodb_metrics
WHERE name ='lock_row_lock_current_waits';
name count
lock_row_lock_current_waits 0
DROP TABLE `t`;
SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
SET GLOBAL innodb_monitor_disable=default;
SET GLOBAL innodb_monitor_reset_all=default;
SET GLOBAL innodb_monitor_enable=default;
disconnect prevent_purge;
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